It's a while since I posted to this thread and somewhere else later on after I had a leaking tank and wrote about it. Here's a brief summary from what I remember:
I have the older (but confirmed replaced) tank with the bolts around the pump flange. I'd stripped it down, removed filler, sender and pump. I noticed curiously that the pump flange gasket was not so good a design as the sender gasket yet both seemed interchangeable.
Re-assembled the tank very carefully using original gaskets, put some gas in tank on the bench and pump flange leaked - WTF*!#?
Repeated the install a couple of times and same thing happened. Checked the tank body which didn't seem to be distorted. ABS thickness check confirmed it was newer tank. Read the bulletin - Replacement tanks have a 5mm wall thickness!
The answer is the pump gasket seems too large for the surface it is sealing so when you position it behind the pump flange it misaligns and you get a gas leak. Why is this? - because if you take their rubber gasket and spill any gas on it or it gets wet before you fit it, it expands. It also gets thinner when fitted a while too.
In the end I used some nitrile rubber sheet I had (3 or 4mm thick I think) and just cut a new gasket and punched the bolt holes, just like the one they used for the sender, but with a generous amount of rubber to fit and align around the inside edge of the hole and outside the pump flange.
I fitted this first time with stainless hex screws and it's been on the bike 8 months with absolutely no leaks.
Here are some info pics to look at (sorry, hadn't realised Macdonge had posted the bulletins)
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